1. Field of the Invention
The instant disclosure relates to a manufacturing method of semiconductor; and more particularly, to a method for adjusting the trench depth on a semiconductor substrate.
2. Description of Related Art
Semiconductor components are becoming smaller and smaller, so that the spacing of the trenches on the substrate is also required to be dramatically reduced in size. When a substrate is etched to form miniature trenches, the reactant or the ion cannot effectively reach the bottom of the substrate, or the product cannot be exhausted easily, so that the etching rate is reduced. The above phenomenon is called the micro loading effect.
As FIGS. 1 and 2 shown, a conventional covering layer 2a is disposed on a substrate 1a. The covering layer 2a defines a narrower spacing d1 and a wider spacing d2. When the substrate 1a is etched, the portion of the substrate 1a corresponding to the narrower spacing d1 is etched to form a shallow trench t1, the portion of the substrate 1a corresponding to the wider spacing d2 is etched to form a deep trench t2. The depth of the shallower trench t1 and the depth of the deeper trench t2 differ by a value h. When the substrate 1a is etched, the portion of the substrate 1a corresponding to the narrower spacing d1 is more likely to suffer the micro loading effect, so that the depth of the trench t1 may be smaller than the depth of the trench t2.